Plastic container

Abstract

A container, especially a bottle, is made from a preform of polyethylene terephthalate (PET), where the preform has a mouth portion, a substantially conical upper portion extending from the mouth portion, and a cylindrical portion extending from the conical portion towards the bottom of the preform and having a substantially uniform wall thickness. When reshaping the preform, the shoulder of the container is formed substantially only of material which in the preform is located in the conical upper portion of the preform, while the cylindrical portion of the container is formed substantially only of material which in the preform is located in the cylindrical portion of the preform. The expansion of the material in the conical portion of the preform and of the material in the cylindrical portion of the preform is selectively controlled in such a manner that the material in the respective portion undergoes stretching in the axial direction of the preform, defined by the quotient of the axial length of the conical portion of the preform and the axial length of the cylindrical portion of the preform having values in the range 0.25-0.35, and by the quotient of the axial length of the shoulder and the axial length of the cylindrical portion of the container having values in the range 0.60-0.80.

I claim: 
     
       1. A container of plastic material made by forming and expanding a preform, wherein said preform comprises a mouth portion, a substantially conical upper shoulder portion extending in an expanding manner from said mouth portion, a cylindrical central portion extending from said shoulder portion, a transitional portion extending from said cylindrical central portion, and a bottom portion extending from said transitional portion and wherein said container comprises a mouth portion, a shoulder portion extending from said mouth portion, a substantially cylindrical central portion extending from said shoulder portion, and a bottom portion extending from said cylindrical portion, the shoulder portion of said container being formed substantially only of plastic material from the conical shoulder portion of said preform, and the central portion of said container being formed substantially only of plastic material from the cylindrical central portion of said preform, wherein a quotient of an axial length of the conical shoulder portion of said preform divided by an axial length of said cylindrical central portion of said preform has values in an approximate range of 0.25-0.35,   a quotient of an axial length of the shoulder portion of said container divided by an axial length of the central portion of said container has values in an approximate range of 0.6-0.8, material of said shoulder portion of said container and said central portion of said container during the expansion being stretched in an axial direction, and   wherein the material in the bottom portion of the container, is substantially non-oriented material, and the central bottom portion of the container, that corresponds to the central portion at the bottom of the preform, has substantially the same shape in the container as in the preform.   
     
     
       2. A container as claimed in claim 1, wherein the material of said conical shoulder portion of said preform is expanded in a circumferential direction wherein the material is given a biaxial stretch which in a region closest to said cylindrical central portion of said container is in an approximate range of 7-15. 
     
     
       3. A container as claimed in claim 1, wherein the material of said conical shoulder portion of said preform is expanded wherein said shoulder portion of said container has a biaxial stretch which is in an approximate range of 2.5-3.6. 
     
     
       4. A container as claimed in claim 1, wherein the material of said conical shoulder portion of said preform is expanded wherein said shoulder portion of said container has a biaxial stretch which is in an approximate range of 2.7-3.4. 
     
     
       5. A container as claimed in claim 1, wherein said conical portion of said preform expands from said mouth portion and has a uniform inner diameter, said conical shoulder portion passes uniformly into said cylindrical central portion, said transitional portion has a same outer diameter, but a smaller inner diameter than said central portion, and wall thickness of said bottom portion is less than wall thickness of said transitional portion. 
     
     
       6. A container as claimed in claim 5, wherein a transition from said central portion of said preform to said transitional portion of said preform is substantially conical in shape. 
     
     
       7. A container as claimed in claim 1, wherein when forming the preform into the container, the material in the bottom portion of the container is deformed without being stretched to such a high degree as to impair the capacity of the material to withstand shrinkage upon heating.